With the remarkable growth of related technologies, a great variety of mobile devices, e.g., smart phones or tablet PCs, are increasingly popular due to their high usability and good portability. Particularly, most recent mobile devices have a touch screen that acts as both an input unit and a display unit through a single screen. Such mobile devices having a touch screen not only offer a traditional communication service, but also offer various new functions such as video playback or document creation.
Additionally, according to recent developments in the speed of a mobile network, a video service executable in the mobile device uses advances in image quality and resolution. This leads to an increase in a touch screen size of the mobile device and to a growing tendency for users to prefer a relatively larger size of the touch screen. Contrary to past mobile devices that merely offer a communication service and have a smaller sized touch screen for a one-handed manipulation, current mobile devices that offer various functions commonly have a larger sized touch screen but may sacrifice one-handed manipulability. That is, a large screen size may often cause users some difficulties in manipulating the touch screen with only one hand.